Circuit breaker



Feb. 13, 1940. Q s JENNlNGs 2,190,517

CIRCUIT BREAKER Original Filed Dec. 17, 1936 2 Sheets-Sheet 1 535 43 /7 d'29. 5 sa /TH ff/ff/ /7 ATTORN EY Feb. 13, 1940. Q Q JENNlNGs Y 2,190,517

CIRCUIT BREAKER Original Filed Dec. 17, 1936 2 Sheets-Sheet 2 ATTORNEY Patented Feb. 13, 1940 UNITED STATES PATENT OFFICE CIRCUIT BREAKER Pennsylvanial Application December 17, 1936, Serial No. 116,324

Renewed July 20, 1939 35 Claims.

My invention relates to circuit breakers in general, and more particularly, to circuit breakers of the type used for controlling lighting and industrial power feeder circuits.

For this type of service, it is particularly desirable to have a circuit breaker which embodies an operating mechanism for moving the contact controlling arm to open and to closed circuit position with a snap action in order to insure quick make and break action. 'I'he contact controlling arn or switch member of the breaker must also be trip-free of the operating handle, i. e., the switch arm must be capable of moving to open circuit position in response to predetermined overload conditions, irrespective of the position of the control handle. As opposed to these struc.

tural and operational requirements, a commercially successful circuit breaker must be moderate in price. Hereto'fore, manufacturers of these devices have endeavored to produce circuit breakers as cheaply as possible, consistent with good quality and ability to meet the requirements. The best of the prior art devices, however, were more costly than would be desired.

It is also desirable that the circuit breaker bei constructed so that it can be easily and cheaply assembled by slidably positioning the parts in recesses in the housing. i

lt is,- accordingly, one of the principal objects of my invention to provide a simple, eillcient and inexpensive circuit breaker which will satisfactorily meet the above-mentioned requirements.

Another object of my invention is to provide an improved circuit breaker structure that utilizes a considerably less number of parts than has heretofore been considered necessary for breakers of the same general type.

Another object of my invention is to provide a simpler operating mechanism and trip arrangement for a circuit breaker which requires fewer parts than devices of the same general type heretofore known or used.

. Another object of my invention is to provide an improved circuit breaker embodying a simple operating mechanism for producing quick makeand-break action and embodying a simple trip ar- (Cl. 20o-116) 'Ihe novel features that I consider characteristic ,of my invention are set forth in particular in the appended claims.l 'I'he invention itself, however, both as to structure and operation, together with additional objects and advantages thereof, will best be understood from the following detailed description of several embodiments thereof when read in connection with the accompanying drawings, in which:

Figure 1 is a vertical sectional view of a circuit breaker embodying the features of my invention, the parts thereof being shown in the closed circuit position;

Fig. 2 is a horizontal sectional view of the circuit breaker show in Fig. 1, taken on the line II--II thereof and looking in the direction of the arrows;

Fig. 3 is a vertical sectional view of the circuit breaker, similar to Fig. 1, but with the parts of the breaker shown in the tripped position;

Fig. 4 is a side elevational view of a modied form of the circuit breaker unit, the parts thereof being shown in the closed circuit position;

and

Fig. 5 is an end elevational view of a group of the circuit breaker units similar to the one shown in Fig. 4 assembled to form a multi-pole breaker or load center device.

Referring to Figs. 1 and 2 of the drawings, the circuit breaker illustrated comprises, in general, a base 1, a cover 9, end terminals II and I3, a stationary or rupture contact I5, a cooperating movable switch arm I1, an operating mechanism indicated generally at I9, and a bimetallic trip element 2|.

The base l is of molded insulating material and is formed to provide a chamber for the switch arm and for a part of the operating mechanism. The cover 9 is also of molded insulating material and has a chamber portion for cooperating with the chamber portion of the base 1. I'he cover 9 is provided with a transverse partition member 23 for dividing the casing formed by the cover 'l and base 9 into an arc chamber 25 and an operating chamber 2l. The side Walls of the base and cover are provided with oppositely disposed aligned grooves 29 for a purpose which Will be hereinafter described.

The left-hand end terminalgl I comprises a at copper strip having an orf-set portion 3|, to the end of which is secured a stationary contact I5. The terminal strip I I is adapted to be secured to the base 1 by means of a screw 33. 'I'he outer end of the terminal strip I I is provided with a threaded opening for the reception of a terminal screw 35 for connecting the terminal to an external electric circuit. I'he right-hand end terminal I3 comprises a flat angular strip of conducting material which has one end portion secured to the base 1 by means of a terminal screw 31 and a nut 39.

The switch arm I1 has a channel-shaped portion I8 the sides of which are provided with openings for mounting the same on a pivot pin 4|. The left-hand end of the switch arm |1 has a movable contact 43 secured thereto in any suitable manner, as for example, by brazing or soldering The right-hand end of the switch arm I1 has a deep notch 45 formed therein to provide a resilient end portion 41.

The operating means for the switch arm comprises, in general. 'a channel-shaped actuating member 49, a toggle type operating handle 5| and an overcenter spring device 53. The actuating member 49 is channel-shaped in cross-section and has depending leg portions 55 each of which is provided with an opening for mounting the ing member formed by the slot 51.

channel-shaped actuating member on the pivot pin 4I. The rearward portion of the switch arm I1 is adapted to normally lie in the channel section of the actuating member 49 between the legs 55 thereof.

The switch arm I1 is normally connected to the actuating member 49 for movement therewith by means of a bimetallic trip element 2|. The trip element 2| comprises a U-shaped strip of bimetallic material, one leg of which is secured to the resilient end portion 41 of the switch arm I1 by any suitable means, as for example, by soldering. The body portion of the bimetallic strip projects through a slot 51 provided therefor in the top of the actuating member 49, and the free end 59 of the strip is disposed in overlapping engagement with a cross piece 6| of the actuat- The free end of the bimetallic strip 2| is electrically connected to the end terminal |3 by means of a flexible shunt conductor 63. It will thus be seen that under normal conditions, the bimetallic trip element 2| serves to connect the switch member I1 to the actuating member 49 for movement therewith. The passage of a predetermined value of overload current through the switch arm and bimetallic element 2| which is connected in circuit therewith, causes the end of the bimetallic element to flex to the right to effect disconnection of the switch arm |1 from the actuating member 49 to effect automatic opening of the circuit in a manner which will be described in connection with the operation of the breaker.

The switch arm I1 is biased to open circuit position by means of a coil spring 65. The spring 65 is coiled about the pivot pin 4I and one end thereof engages against the base 1 while the other end engages the underside of the switch arm I1.

'I'he operating handle 5I is formed of molded insulating material and is provided with a pivot pin (i1,` which is of slightly greater length than the width of the operating handle. The handle 5| has a portion 69 which projects through an opening 1| formed in the top of the cover 9, and with a depending portion 13. An end support 15 for the overcenter spring device 53 is pivotally connected to the depending portion 13 of the operating handle 5| by means of a Apivot pin 11. 'I'he overcenter spring device 53 consists of a pair of concentric coil springs 19 and 8|. A'I'he upper ends of the springs engage the end support 15 while the lower ends thereof engage an end support 83 which `liaise. notch 85 formed therein for pivotally mountingv lthe same on. a cross-piece 81 of the 'actuating member 48.

The bottoms of the grooves29 in the side walls 'of the operating handle 5I and the overcenter coil spring device 53 thus forms a mechanism similar to s pair of toggle linksV and an overcenter spring.

The circuit for the breaker extends from the left-hand end terminal to the stationary contact I5, movable contact 43, switch arm I1, bimetallic trip element 2| and through the flexible shunt conductor 63 to the right-hand end terminal I3.

A U-shaped arc shield 89 is disposed in the arc chamber 25 in order to deionizeand quickly extinguish the arc formed between the stationary and movable contact when the circuit is opened, and also to protect the side walls of the arc chamber from damage by the arc.

The operation of the circuit breaker is as follows. Fig. 1, let itbe assumed that itis desired to manually open the circuit controlled by the breaker. To open the circuit; the operating handle 5| is moved in a clockwise direction from the closed circuit position shown in Fig. 1 to the open circuit position at the opposite end of the opening 1|'. During the first part of the clockwise rotation of the operating, handle 5| about its pivot pin 61, the coil springs 19 and 8| are compressed until the pivot pin 11 of the upper spring end support crosses the line joining the center of the pin 61 and the point-of engagement of the spring end support with the cross-piece 81 of the actuating member 49. At this instant, the toggle formed by thev depending portion 13 and the overcenter spring device 53 is in the equilibrium position. The instant that the pin 11 moves to the left of the line joining the pin 61 and the point of engagement of the end vsupport 85 with the cross-piece 81, the handle 5I is automatically moved with a snap action to its open circuit With the parts in the position shown in position. After the pin 11 is moved to the left of the imaginary line mentioned, the force exerted by the springs 19 and 8| tending to hold the contact arm |1 in closed circuit position progressively decreases until it becomes less than the force exerted by the biasing spring 65. At this instant the line of action ofthe springs has moved to the left of a line joining the center of the pivot pin 4| and the cross-piece 81 so that the force exerted by the springs 19 and 8| and also the force exerted by the spring 65 moves the switch Iarm I1 in a clockwise direction about its pivot pin to its open circuit position with a snap action. In the open circuit position, the pin 11 occupies a position to the left of the center line joining the pins 61 and 4| at a per'- pendicular distance therefrom equal to the cor-- responding distance therefrom that the pin occupies in the closed circuit position of the operating handle.

In closing the circuit breaker substantially the reverse action takes place. To close the breaker,

the operating handle 5| is moved from its open circuit position in a counter-clockwise direction about its pivot pin 61 to the c1osed circuit position shown in Fig. 1. During movement ofthe operating handle to the closed circuit position, the pivot pin 11 moves past the center line joining the pivot pin 61 and the cross-piece 01. After the pin 1 1 crosses this center line, the springs 19 and 8| move the handle 5| automatically and with a snap action to its closed circuit position. At a certain point in the movement of the springs 19 and 9|, their line of action moves to right of a line joining the center of the pivot pin 4I and the cross-piece 01 and the force exerted by these springs then moves the switch arm I1 in a counter-clockwise direction about the pin 4| toits closed circuit position with a snap action. 'Ihe force exerted by the springs 19 and 9| is considerably greater than that exerted by the spring 65 and produces a large contact pressure between the contacts I5and 43 to insure a good l electrical connection therebetween.

With the parts of the circuit breaker in the closed circuit position shown in Fig. 1, if an overload of predetermined magnitude and sufilcient duration occurs in the circuit controlled by the breaker, the overload current heats the bimetallic trip element 2| and causes the free end 59 thereof to disengage the cross-piece 6|' of the actuating member 49. The disengagement of the free end 59 of the bimetallic trip element 2| from the cross-piece 0I of the `actuating member releases the switch arm I1 from its connection to the actuating member 49. Following the release of the switch arm from its connection with the actuating member 49, the biasing spring 65 moves the switch arm I1 in a clockwise direction about its pivot pin 4| to the open circuit position, as shown in Fig. 3. The circuit controlled by the breaker is thus automatically opened in response to predetermined overload conditions. l To reset the breaker after a tripping operation has occurred, the operating handle is moved from the closed circuit position to the open circuit position, which causes the actuating member 49 to be rotated in a clockwise direction about its pivot pin 4| until the cross-piece 6I thereof reengages under the end 59 of the bimetallic trip element 2| after it has cooled and returned to normal position. After the breaker has thus been reset, as described, the circuit breaker may be closed again by manually moving the operating handle 5| to its closed circuit position, since the engagement of the bimetallic trip element 2| with the cross-piece 6| of the actuating member 49 has reestablished the connection between the switch arm I1 and the actuating member 49.

The trip characteristic of the circuit breaker may be adjusted by means of an adjusting screw 9| which is threaded through the bimetallic element 2| and the resilient end portion 41 of the switch arm I1. 'I'he end of the screw 9| engages the solid wall of the notch and by turning the screw 9| in a clockwise direction, the resilient end portion 41 is moved a small distance to the right so as to increase the amount of overlap between the free end portion 59 of the trip element 2| and the cross-piece 6I of the actuating member 49. Increase in the amount of overlap between the free end 59 ofthe trip element 2| and the cross-piece 6| increases the value of overload current necessary to effect a tripping operation or increases the time interval between the occurrence of the overload and the tripping action on lower magnitude overloads.

The cover 9 is adapted to be removably mounted on the base 1 by means of bolts (not shown) which pass through aligned openings 93 provided in the base 1 and cover 9. The removable mounting of the cover 9 and the vertical grooves 29 in the side walls oi' the cover 9 and base 1 for the reception of the pivot pins 01 and 4| provides a structure whereby the parts of the circuit breaker may be quickly and easily assembled or disassembled for adjustment, repair or replacement purposes.

In Fig. 4 is shown a modified form of circuit breaker embodying the features of my invention. In this form of the invention the structure of the end terminals.. the stationary contact, the switch arm, the actuating member and the trip element are identical to the corresponding parts of the embodiment shown in Figs. l and 2 and described in connection therewith. Consequently, the same reference characters have been used wherever applicable and only a brief description of these partswill be given.

Referring to Fig. 4, the circuit breaker comprises, in general, an open-sided casing section 95, end terminals II and I3, a stationary or rupture contayfc't I5, a co-operating movable switch arm I1, aichannel-shaped actuating member 49. a bimetallie trip element 2|, an operating handle 91, and an overcenter spring 99.

'I'he casing section 95 is formed of a single piece of molded insulating material and has the same general cross-sectional outline as the casing formed by the base 1 and cover 9 in the modification shown in Figs. 1 and 2. The casing section 95 is open at one side and its side wall is provided with a projecting pivot stud |0| for forming a pivot support for the switch arm I1 and the actuating member 49. A second pivot stud |03 projects from the side wall of the casing and forms a means for pivotally mounting the operating handle 91. Each of the end walls of the casing section 95 is provided with a. slot |05 forslidably receiving the end terminals II and I3. The top of the casing section 95 is provided with a recess |01 for the reception of the operating handle 91, and a portion of the handle |09 projects outwardly through the top of the recess In this modification of the invention, the switch arm I1 is normally connected to the channelshaped actuating member 49 by means of the bimetallic trip element 2| in the same manner as was described in connection with the embodiment shown in Figs. 1 and 2. The switch arm is biased to its open circuit position by means of a coil spring 65.

The operating means for moving the actuating member 49 and the normally connected switch member I1 to open and to closed circuit position comprises the operating handle 91, and the overcenter spring 99. The operating handle 91 has a notch III formed in the lower end thereof for receiving the upper end of the spring 99. The spring 99 is of the leaf type and has a reduced lower end portion |I3 which is adapted to pass through an opening I I5 formed in the cross-piece 81 of the actuating member 49. The shoulders of the spring 99 formed by the reduced portion II3 thus pivotally engage the top of the cross-piecev 89 to form a pivotal connection between the spring 99 and the actuating member 49. The

length ofthe spring 99.is greater than the distance between its point of engagement with the bottom of the notch of the operating handle 91 and its point of engagement with the actuating member 49. so that it is held in stressed or bowed condition :1s shown in Fig. 4.

All ofthe parts ol the circuit breaker are adapted to bc removably mounted in the open-'sided casing section through the open side thereof. The end terminals II and I3 are adapted to be slid into the notches I05 formed in the end Walls of the casing and are retained in operative position by means of the screws 33 and 31. The biasing spring 65, the switch arm I1, and the actuating member 49 are adapted to be inserted through the open side of the casing and mounted on the proiecting pivot stud IOI. The operating handle 91 is also adapted to be inserted through the open side of the casing section for mounting on the `projecting pivot stud |03. The lower end ofthe over-center spring 99 is inserted through the open side of the casing section into the opening I I5 in the cross-piece 81 of the operating member 49, and the spring is bowed and its upper end pushed into the notch I'I I of the operating member 91. It will thus be seen that all of the parts of the' cir-- cuit breaker may be readily and easily assembled or disassembled, through the open side of the casing section.

The operation of this modification of the invention is substantially similar to that of the embodiment shown in Figs. 1 and 2. With the parts in the closed circuit position, as shown in Fig. 4, let it be assumed that it is desired to open the circuit controlled by the breaker. To open the circuit. the operating handle 91 is moved in a clockwise direction about its pivot stud |03.. At a certain point in the clockwise rotation of the operating handle, the leaf spring 99 snaps overcenter to automatically move the handle 91 to its open circuit position and to rotate the actuating member 49 and normally connected switch member I1 in the clockwise direction about their pivot stud IUI to their open circuit position, with a snap action in substantially the same progressive man* ner as was described in connection with the embodiment shown in Figs. 1 through 3.

In closing the circuit breaker substantially the reverse action takes place. The operating handlel is moved from the open circuit position in a counter-clockwise direction to the closed circuit position shown in Fig. 4. At a certain point in the movementl ol' the operating handle the leaf spring 99 passes its point of equilibrium and snaps over-center to automatically move the operating handle v91 to its closed circuit position rand to rotate the actuating member 49 and normally connected switch arm I1 in a counter-clockwise direction about the pivot stud IOI to their closed circuit position with a snap action in substantially the same progressive manner as was described in the operation of the embodiment shown in Figs. 1 through 3. 'Ihe leaf spring 99 provides a means for securing quick make and quick break action during the manual operation of the circuit breaker. With the parts in the closed circuit position shown in Fig. 4, the endwise thrust or force exerted by the leaf spring 99 is sufficient to hold the switch arm I1 in closed circuit position and to provide a definite contact pressure between the movable contact and the stationary Contact in spite of the biasing action of the spring 65 since the force exerted by the spring 99 is considerably greater than that exerted by the spring 65.

The tripping operation of this modication of the invention is identical with the tripping operation described in connection with the embodiment shown in Fig. 1. When an overload of predetermined magnitude and duration occurs in 9.1 is moved to the open circuit position which causes the actuating member 49 to rotate inthe clockwise direction about the pivot pin IOI to effect reengagement of the free end of the bimetallic trip element 2I with the cross-piece 6I of the actuating member 49. The connection between the switch member I1 and the actuating member 49 is thus re-established and the circuit breaker may be manually closed by moving the operating handle to closed circuit position.

The casing section 95 of the circuit breaker is provided with a plurality of transverse openings II1. If the circuit breaker is to be used individually, a cover plate or cooperating casing section I I9 is placed over the open side of the casing section 95 and secured thereto by means of bolts which pass through the openings H1. The cover plate section H9 acts to hold the parts in their mounted position within the casing and seals the casing against the entrance of dirt or moisture. As shown on the drawings, the joint or division plane between the two members or sections of the insulating housing is generally parallel with the plane of movement of the movable contact, which means that the two members or sections are separable sidewise. This is an important difference from the type of two-section casing shown in Figs. 1, 2 and 3, because all of the parts may be assembled through the open side of one casing section, and also because it provides maximum visibility and accessibility of the parts for purposes of inspection'and adjustment after the breaker is completely assembled and before the covering member of the casing is put in place. If desired, a number of the circuit breaker units shown in Fig. 4 may be mounted side-by-side in a group, as illustrated in Fig. 5. In such case, elongated bolts pass through the aligned openings II'I of the units and secure the units together and the cover plate I I9 over the open side of the end unit. When the units are secured together to form a group, as shown in Fig. 5, the side wall of each unit acts to close the open side of th'e adjacent unit, and to retain the parts thereof in their mounted position. The grouped circuit breaker units may be used as a multi-pole circuit breaker or as a load center device.

It will thus be seen that I have provided an eicient and simple circuit breaker structure that lio utilizesa minimum number of parts and that can be manufactured at a low cost. The circuit breaker structure also embodies the desirable quick make-and-break action and may be easily assembled or disassembled for adjustment, repair or replacement purposes.

While I have shown and described several embodiments of my invention in accordance with the patent statutes, it is obvious that various changes may be made in the structural details without departing from the spirit of the invention. I desire, therefore, that the invention be limited only by the reasonable construction of the language of the appended claims and by the prior art.

I claim as my invention:

1. In a circuit breaker, a movable switch arm biased at all times to open circuit position, an independently movable actuating member, means including a current-responsive device for normally connecting said switch arm to said actuating member for movement thereby, operating means including an operating handle mounted for movement relative to said actuating member, and an overcenter spring connecting said handle to said actuating member for moving said actuating member and normally connected switch arm to open and to closed circuit position with a snap action to open and to close the circuit, said current-responsive device being operable in response to predetermined conditions to release said switch arm from said actuating member to permit said switch arm to move to open circuit position independently of the position of said handle. 2. In a circuit breaker, a movable switch arm having a spring biasing it to open circuit position, an independently movable actuating member, means including a bimetallic element for normally connecting said switch arm to said member for movement thereby, operating means including an operating handle mounted for movement relative to said actuating member, and a second spring between said handle and` said member for moving said member and normally connected switch arm to open and to closed circuit position with a snap action, said bimetallic element being operable in response to predetermined conditions to release said arm from said member to allow said arm to be moved by its spring to open circuit position independently of said second spring.

3. In a circuit breaker, a switch arm mounted for pivotal movement-about a ilxed axis only, means biasing said arm to open circuit position, an actuating member pivoted to move only about the same axis as said arm, means including a bimetallic element connected in circuit with said switch arm for normally connecting said arm to said member for movement therewith, operating means including an operating handle mounted for movement relative to said actuating member, and an overcenter spring for moving said member and connected switch arm to open and to closed circuit position with a snap action, said bimetallic element being operable in response to abnormal circuit conditions to effect disconnection of said arm from said member to allow said biasing means to move said arm to open circuit position independently of the position of said operating means.

4. In a circuit breaker, a pivotally mounted switch member, means biasing said member to open circuit position, a movable actuating member, means including a bimetallic element having one end secured to said switch member for normally connecting said members for movement together, operating means including an operating member mounted for movement relative to said actuating member, and an overcenter spring for moving said normally connected members to open or to closed circuit position with a snap action even if the said operating member is moved slowly throughout its range of movement, said bimetallic element being operable in response to abnormal conditions to release said switch member from said actuating member to allow the rst said biasing means to move said switch member to open circuit position irrespective of the position of said operating means and without requiring movement of said actuating member.

5. In a circuit breaker, a switch member mounted for pivotal movement about a single tlxed axis and biased to open circuit position, an actuating member pivoted for movement only about the same axis as said switch member, means including a bimetallic strip having one end secured to one of said members, for normally connecting said members for movement together, operating means for moving said Anormally connected members to open and to closed circuit position with a snap action, said bimetallic strip being operable in response to predetermined conditions to release said switch member from said actuating member to allow said switch member to move to open circuit position.

6. In a circuit breaker, a switch member mounted for pivotal movement about a single fixed axis, means biasing said member to open circuit position, a movable actuating member having a single xed axis, means including a bimetallic element connected in the circuit controlled by the breaker and having one end secured to one of said members for normally connecting said members for movement together, a manually operable snap acting mechanism for moving said normally connected members to open and to closed circuit position with a snap action, said mechanism causing said switch member to remain in either position during operation of the mechanism until the mechanism snaps, said bimetallic element being flexed in response to predetermined overload conditions to disengage its free end from said other member for disconnecting said members to allow said biasing means to move said switch member to open circuit position.

7. In a circuit breaker, a switch member mounted for pivotal movement about a single xed axis, means biasing said member to open circuit position, a movable actuating member, means including a bimetallic element connected in the circuit controlled by the breaker and having one end secured to one of said members for normally connecting said members for movement together, a snap acting mechanism including a,

movable operating handle for moving said normally connected members to open and closed circuit position with a snap action irrespective of how slowly said operating handle is moved throughout its range of movement, said bimetallic element being iiexed in response to predetermined overload conditions to disconnect said members to allow said biasing means to move said switch member to open circuit position even though said actuating member may be prevented from moving.

8. In a circuit breaker, a base, a switch arm pivotally mounted on said base and biased to open circuit position, an actuating member pivotally mounted on said lbase about the same axis as said arm, means including an electro-responsive device for normally connecting said arm to said member for movement therewith, operating Imeans comprising a pivotally mounted toggletype operating handle, and a compression spring having one end pivotally connected to said handle and its other end pivotally engaging said actuating member, for moving said member and normally connected arm to open or to closed circuit position with a snap action, a cover mounted on said base provided with an opening through which projects a portion of said handle, said electro-responsive device being operable in response to abnormal overload conditions to disconnect said arm from said member to allow said arm to move to open circuit position irrespective of the position of said operating handle and spring'.

9. In a circuit breaker, a chambered base, a pivot pin disposed transversely between the side walls of said base, a switch arm pivotally supported by said pin and biased to open circuit position, an actuating member pivotally supported by said pin, means including an electro-responsive device for normally connecting said arm to said member for movement therewith, a cooperating chambered cover for said base, a toggle type operating handle pivotally supported between the side walls of said cover aboutan axis parallel to and substantially above that of said pivot pin, said handle having its upper end extending through an opening provided therefor ingthe top of said cover, an overcenter compression spring having one end pivotally coupled to the lower end of said handle and its lower end pivotally coupled to said actuating member, said handle 'being movable to an openor to a closed circuit position to move said member and normally connected arm to an open or to a closed circuit position with a snap action, said electro-responsive device being operable in response to predetermined conditions to disconnect said arm from said member to allow said arm to move to the -open` circuit position irrespective of the position of said handle.

10. In a circuit breaker a pivotally mounted switch arm, means biasing said arm to the open circuit position, an actuating member pivoted about the same axis as said arm, means including a bimetallic element for normally connecting said arm and said member for movement ltogether, operating means including a pivotally mounted operating handle and a stressed leaf spring between said handle and said actuating member for moving said member and normally lconnected switch arm to open and to closed circuit position with a snap action, said bimetallic element being operable in response to predetermined conditions to disconnect said arm from said member to allow said biasing means to move said arm to open circuit position.

11. In a circuit breaker, a pivotally mounted switch arm, an actuating member pivoted about the same axis as said switch arm, means including a bimetallic element for normally connecting said arm to said member for movement therewith, operating means comprising a pivotally mounted operating handle having a bifurcated end portion, a leaf spring having one end engaged in the bifurcation of said handie and its other end engaging a point of said member between the pivot axis thereof and the pivot axis of said handle, the length of said spring being greater than the distance between its points of engagement with said handle and said member so `.that it is held in stressedbowed condition, said operating handle being movable to open or to closed circuit position to cause said spring to move said actuating member and normally connected arm to open or to closed circuit position with a snap action, said bimetallic element being operable in response to a predetermined condition to release said arm from its connection with said member.

12. In combination, a plurality of individua circuit breaker units, each of said units compris- `ing an open-sided casing, end terminals for connecting the unit in an electrical circuit, contact means, operating means for said contact means, and means for removably mounting said end terminals, said contact means and said operating means in said casing through the open side thereof, means for securing said units together so that the side wall of each unit, but one, closes the open side of the adjacent unit and retains the parts ther eof in mounted position.

13. The combination of a plurality 'of individual circuit breaker units, each of said units comprising an open-sided casing, a stationary contact, a cooperating movable switch arm, operating means for moving said switch arm to open and to closed circuit position, a trip device for causing said switch arm to move to open circuit position in response to predetermined overload conditions, end terminals for connecting the unit in an electrical circuit, and means for removably mounting said parts in said casing through the open side thereof, means for securing said units together, so that the side wall of each unit closes the open side of the adjacent unit and retains the parts thereof in mounted position, and a cover plate for the open side of one end unit.

14. A circuit breaker unit comprising a casing of insulating material, a pivotally mounted switch member, means biasing said member to open circuit position, an actuating member pivoted about the same axis as said switch member, means including an electro-responsive device for normally connecting said members for movement together, operating means including an operating member mounted for movement relative to said actuating member, and an overcenter spring for moving said actuating member and the normally connected switch member to open and to closed circuit position with a snap action, said electro-responsive device being operable in response to predetermined conditions to effect disconnection of said'switch member from said actuating member to allow said biasing means to move said switch member to open circuit position, said operating member being pivotally mounted in bearings provided in the insulating material of said casing.

l5. A circuit breaker unit comprising, in combination, an open-sided casing, a stationary contact, a cooperating movable switch member, operating means ,for moving said switch member to open and to closed circuit position, a trip device operable in response to predetermined conditions to cause said switch member to move to open circuit position independently of said operating means, terminals for connecting said unit in an electrical circuit, said casing being provided with means for slidably receiving said abovementioned parts whereby said parts are removably mounted in said casing through the open side of said cas- 16. In a circuit breaker, a chambered base, a cooperating chambered cover, said base and cover forming a split casing, the side walls of said base and cover being provided with oppositely disposed aligned grooves, a contact controlling arm mounted on a transverse pivot pin which is removably mounted in the grooves of said base, the ends of said pin being rotatably supported by the bottom ends of said grooves, operating means for moving said arm about its pivot pin to open and to closed circuit position vwith a snap action to vopen and `to close the circuit comprising a toggle type operating handle having a portion adapted to project through an opening in the top of said cover and a transverse pivot pin, an overcenter spring connected to said handle and to said arm at a point above the pivot pin of said arm, the pivot pin of said handle being removably mounted in the grooves of said cover so that its ends are rotatably supported against the top ends of said grooves, said spring being held in compressively stressed condition between said handle and arm to hold the ends of said pivot pins against the ends of said grooves.

17. In a circuit breaker, a contact arm mounted for pivotal movement about a xed axis, means biasing said arm to open position, an independently movable actuating member, means including an electro-responsive device for normally connecting said contact arm to said actuating membeifor movement thereby, operating means includingA an operating member mounted for movement relative to said actuating member, and an overcenter spring for moving said actuating member and normally connected contact arm to open and to closed position with a snap action, said electro-responsive device being operable in response to predetermined conditions to ell'ect release of said contact arm from said actuating member to permit movement of said contact arm Ato open position by the first said biasing means independently of said overcenter spring.

18. In a circuit breaker, a pivotally mounted switch member, means biasing said member to the open circuit position, a movable actuating member, means including a bimetallic element for normally connecting said switch member to said actuating member for movement thereby, operating means including a manually operable operating handle for moving said normally connected members to open and to closed circuit position with a snap action even though said handle is moved slowly throughout its range of movement, said bimetallic element being operable in response to predetermined conditions to release said switch member from said actuating member to permit said switch member to be moved to open position by the iirst said biasing means irrespective of the position of said handle and independently of said overcenter spring.

19. The combination in an automatic circuit breaker, of a rupture contact, a movable contact member provided with a contact engageable with the rupture contact, a manually movable operating member, mechanism including means operative upon movement of the operating member to cause movement of the contact member and including an element adapted to cause opening of the contact member independent of any control of the operating member upon the attainment of abnormal current conditions in the circuit, and a two-piece insulating housing enclosing all of the aforesaid parts other than the manuall engageable portion of the operating member and having the division plane between the two pieces parallel with the direction of movement of the contact member, the said housing having means for tixing the path of movement of the contact memberandfor pvotally supporting the operating member, and the said housing being free from positive connection with any substantially movable parts so that when the two pieces of the housing are assembled the said parts are movably held between them and so that when the sections are separated the said movable parts are readily separable therefrom."

20. In an automatic circuit breaker, the combination of a rupture contact, a contact member movable and provided with a contact surface engageable with the rupture contact, a manually movable operating member, mechanism including means operative upon movement of the operating member to cause movement of the movable contact member and including an element adapted to cause opening of the movable contact member independent of the operating member upon the attainment of abnormal current conditions in the circuit, and a housing enclosing all o1' the aforesaid parts other than the manually engageable portion of the operating member and comprising two pieces of insulating material having the joint between them generally parallel with the plane of movement of the movable contact member, the said housing having a plurality of means each serving as the supporting and movement deiining means for one of the aforesaid parts and said housing being free from positive connection with any substantially movable parts so that it is only when the two pieces are assembled together that the said substantially movable parts are positively held in operative relation.

21. In an automatic circuit breaker, the combination of a rupture contact, a contact member movable and provided with a contact surface engageable with the rupture contact, a manually movable pivoted operating member, mechanism including means operative upon movement of the operating member to cause movement of the movable contact member and including any element movable toy initiate opening movement of the movable contact member independently of the operating member upon the attainment of abnormal current conditions in the circuit, and an insulating housing enclosing all of the aforesaid parts other than the manually engageable portion of the operating member and comprising two members having the joint between them extending generally in the same direction as the plane of movement of the movable contact member, at least one of the said insulating housing members serving as the frame of the'circuit breaker'and having means movably supporting the movable contact member and the pivot of the operating member without said movable contact member and said operating member being positively fastened to said housing member, and the said housing member receiving said movable parts through its open' side at said joint so that when the housing members are assembled the said parts are held between` them.

22. In an automatic circuit breaker, the combination of a rupture contact, a contact member movable and carrying a contact surface engageable with the rupture contact, a manually movable operating member, mechanism operatively connecting the operating member with the movable contact member and including an element movable to permit opening movement of the movable contact member independently of the operating member upon the attainment of abnormal current conditions in the circuit, and an insulating housing enclosing all of the aforesaid parts other than the manually engageable portion of the operating member and comprising two members of insulating material having the joint between them generally parallel with the plane of movement of the movable contact member, and at least one of the said insulating members serving as at least part of an insulating frame individually supporting the movable contact member and the operating member without being positively fastened thereto. Y

23. In an automatic circuit breaker, the cornbination of a rupture contact, a contact member movable and provided with a contact surface engageable with the rupture contact, a manually movable operating member, mechanism including means for operatively connecting the operating member with the movable contact member and said mechanism being movable to permit opening movement of the movable contact member independently of the operating member upon the attainment of predetermined current conditions in the circuit, an insulating housing enclosing all of the aforesaid parts other than the manually engageable portion of the operating member and comprising two parts having the joint between them generally parallel with the plane of movement of the movable contact member, and at least one of said parts of the housing having means for slidably receiving said movable contact member, said operating member and said mechanism,

and said movable contact member and said operating member being supported on said part of the housing by said means for slidably receiving them without being fixedly secured thereto.

24. In an automatic circuit breaker, the combination of a rupture contact, a movable contact "member provided with a contact surface engageable with the rupture contact, a manually movable operating member, mechanism operatively connecting the operating member with the movable contact member, said mechanism permitting opening movement of the movable contact member independently of the operating member upon the attainment of abnormal current conditions in the circuit, a pair of terminal members, one of said terminal members carrying said rupture contact and the other of said terminal members being electrically connected to said movable contact member, an insulating housing enclosing all of the aforesaid parts except the manually engageable portion of the operating member and the terminal ends of said terminal members, said housing comprising two members having the joint between them generally parallel with the direc-- tion of movement of the contact member, at least one of said housing members serving as an insulating frame and having an open side, a closed side and means'for receiving each of said parts through its open side, and said housing members having means serving to individually support said operating member and said movable contact member in position but having only readily detachable connection therewith.

25. The combination in an automatic circuit breaker, of a rupture contact, a movable contact carrying member provided with a contact engageable withthe rupture contact, a manually movable operating member, mechanism normally operatively connecting the operating member with the contact carrying member and including a bimetallic member connected at one end to and movable with the movable contact and an actuating member connectable to the movable Contact v carrying member and movable upon movement of said operating member to normally actuate said movable contact, said actuating member being normally latched by the other end of said bimetallic member and being releasable from the bimetallic member upon the occurrence of a predetermined condition to permit opening of said movable contact independently of the said operating member, a pair of terminal members, one of said terminal members carrying said rupture contact and the other of said terminal members being connected by a exible shunt to said other end of the bimetallic member, a two-piece insulating housing enclosing all of the aforesaid parts other than the manually engageable portion of the operating member and the terminal ends of said terminal members, the joint between said two pieces of the housing extending generally parallel with the direction of movement of the contact member, and at least one of said pieces of the housing serving as at least partof an insulating frame and having means for receiving the connected unit including said movable contact carrying member, said actuating member, said bimetallic member and the terminal member connected thereto by the iiexible shunt, and said insulating frame also having means for separately receiving and supporting said operating member and the terminal member carrying the rupture contact, and said movable contact carrying member, said actuating member, said bimetallic member and said operating member all being free of positive connection with either piece of the insulated frame.

26. The combination in an automatic circuit breaker, of a stationary rupture contact, a movable contact member provided with a contact engageable with the rupture contact, a manually movable operating member, mechanism operatively connecting the operating member with the contact member and including an element adapted to release the contact member from the control of the operating member upon the attainment of abnormal current conditions in the circuit, a two-section insulating housing enclosing all of the aforesaid parts other than the manually engageable portion of the operating member and having the division plane be- .tween the two sections parallel with the direc- `tion of movement of the contact member,

the said housing sections serving as the sole means for supporting the contact member for movement and for pivotally supporting the operating member and the said sections being free from positive connection with any movable parts so that when the sections are assembled the said parts are movably held between them and so that when the sections are separated the said parts are readily separable therefrom, and a metallic element carrying the rupture contact and connected to at least one of the housing sections.

27. A circuit breaker unit comprising, in combination, an open-sided casing, a stationary contact, a cooperating movable switch member, operating means for moving said switch member -to open and to closed circuit position, a trip device operable in response to predetermined conditions to cause said switch member to move to open circuit position independently of said operating means, terminals for connecting said unit in an electrical circuit, said casing being provided with means for slidably receiving said above-mentioned parts whereby said parts are removably mounted in said casing through the open side of said casing, a second casing member for completing thecasing and holding the abovementioned parts therewithin, and the joint in the completed casing extending in the same general direction as the plane of movement of said movable switch member.

28. A circuit breaker comprising, in combination, an open-sided casing member, a contact, a switch member having a Contact surface movable to engage and disengage the first said contact, operating means including a handle for moving said switch member to engaged and disengaged positions, a trip element operable in response to predetermined conditions to cause `said switch member to move to disengaged posifrom each other'in the direction perpendicular to the Vplane of movement of said switch member and at least one -of them serving as an taining said contact, saidswitch member and said handle without being securely fastened thereto.

29. A circuit breaker comprising, in combination, an open-sided casing member of insulating material, a first contact, a cooperating movable switch member provided with a second contact engageable with said rst contact, operating means including a. manually operable member for moving said switch member to open and to closed circuit position, a trip element operable in response to predetermined conditions to initiate movement of -said switch member to open circuit position irrespective of the position in which said manually operable member may be held, a second casing member of insulating material engaging the iirst said casing member at a joint extending in the same general direction as the plane of movement of said switch member, the rst said open-sided casing member receiving at least some of the aforesaid parts through its open side, and said casing members forming the enclosure for the circuit breaker and at least one of said casing members also forming the frame of the circuit breaker having means by which said first contact, said switch member and said manually operable member are individually mounted by being merely placed in position in engagement with said mounting means.

30. In a circuit breaker, an open-sided casing member of insulating material, a terminal strip having a contact thereon, amovable switch member having a contact thereon for engaging the contact on the terminal strip, operating means including a manually operable member for moving said switch member to open and to closed circuit position and a bimetallic element operable in response to predetermined conditions to initiate movement of said switch member to open circuit position irrespective of the position in which said manually operable member may be held, a second terminal strip having the bmetallic member connected in series therewith, a second casing member of insulating material, one of said casing members having means for slidably receiving said movable switch member and said operating means, said casing members having theirmeeting edges so positioned as to be assembled together by movement toward each other in a direction perpendicular to the plane of movement of said switch member, said casing members of insulating material forming the frame of the circuit breaker and having both said switch member and said manually operable member individually supported thereon for operative movement and being readily separable therefrom, and said casing members enclosing all of the aforesaid parts except the terminal ends of said terminal strips `and one end of said manually operable member.

31. In a circuit breaker, an open-sided casing member of insulating material, a terminal strip having a contact mounted thereon, a movable switch member having a Contact thereon for engaging the contact on the terminal strip, operating means including a manually operable member, and a bimetallic member connected at one end to said switch. member to move therewith and electrically connected in series with the contact on the switch member, said bimetallic member having its other end normally in latching engagement with said actuating member to cause said switch member to move upon movement of said operating member and said bimetallic member being releasable from said actuating member upon the occurrence of a predetermined -abnormal condition to permit opening of the switch member independently of the position of said manually operable member, a second terminal strip having a flexible conductor secured at one end thereto for connecting said bimetallic member in series therewith, a second casing member of insulating material cooperating with the rst said easing member for forming a. divided enclosure for all of the aforesaid parts other than the operating end of said manually operable member and the terminal ends of said terminal strips with the joint between said casing members extending in the same general direction as the plane of movement of said switch member, and at least one of said casing members acting as an insulating frame for the circuit breaker and supporting at least all of the aforesaid parts other than said terminal strips in operative relation without being separately fastened thereto.

32. A circuit breaker unit comprising, in combination, an open-sided casing, a contact, a cooperating movable switch member, operating means for moving said switch member to open and to closed circuit position, a trip device operable in response to predetermined conditions to cause said switch member to move to open circuit position independently of said operating means, terminals for connecting said unit in an electrical circuit said casing being provided with means for slidably receiving at least a. majority of the above-mentioned parts through the open side of said casing, and a closure member having a substantially plane surface on one side engaging said open-sided casing with said plane surface lying at one side of the aforesaid parts and generally parallel to the'plane of movement of said switch member, said closure member being the only means for securing a majority of the aforesaid parts in postion with said means for slidably receiving them in the open-sided casing.

.33. In an automatic circuit breaker, the combination of a pair of terminal members, a first contact electrically connected to one of said terminal members, a movable contact carrying member provided with a contact surface engageable with the said iirst contact, a manually movable operating member, means for operatively connecting the manually movable operating member to the movable contact carrying member with a readily separable connection between said means and said manually movable operating member, said means being movable to permit opening movement of the movable contact carrying member independently of the manually movable operating member upon the attainment of predetermined current conditions in the circuit and including a bimetallic element mounted and electrically connected at one end on said movable contact carrying member and having a flexible conductor connecting its other end directly to the other of said terminals, an insulating housing enclosing all of the aforesaid parts other than the manually engageable portion of the manually movable operating member and the terminal ends of said terminal members, said insulating housing comprising two parts having the joint between them extending in the same general direction as the plane of movement of the movable contact carrying member and at least one of said parts of the housing having means for slidably receiving the connected unit including the rst said contact and terminal, the unit including said movable co'ntact carrying member, said binietallic member, said flexible conductor and said other terminal, and the unit including said manually movable operating member, and said movable contact carrying member and said manually movable operating member being secured to said one part of the housing only by being slipped into engagement with said means for slidably receiving them and by securing the two parts of the housing together.

34. In a circuit interrupter, a rst assembly unit including a terminal strip having means for securing a conductor thereto adjacent one end thereof and a contact surface adjacent the other end thereof, a second assembly unit including a manually movable operating member, a third assembly unit including a movable contact carrying member, a bimetallic element mounted and electrically connected at one end on said movable contact carrying member and a second terminal having means for securing a conductor thereto at one end and connected by a fiexible portion to the other end of said bimetallic element, and a `housing in which said three assembly units are mounted in operative relation without being xedly secured to each other and with said contactcarrying member movable in response to movement of said manually movable operating member to both make and break the circuit and movable upon ilexing of. said bimetallic element to break the circuit irrespective of the position in which said manually movable operating member is lield, said housing including two members of insulating material having-means for slidably receiving said three assembly units with the jointbetween the two members extending generally parallel to the plane of movement of said contact carrying member.

35. A circuit breaker unit comprising, in combination, an open-sided casing, a stationary contact, a cooperating movable switch member, operating means for moving said switch member to open and to closed circuit position, said operating means including a pivoted handle member and an over-center spring having its line of action movable across the pivot of the handle member and acting when in.closed position to bias said switch member into. engagement with said stationary contact and acting when in open position to bias said switch member to open position, a trip device operable in response to predetermined conditions to cause said switch member to move to open circuit position independently of said operating means, terminals for connecting said unit in an electrical circuit, said casing being provided with means for slidably receiving said above-mentioned parts whereby said parts are removably mounted in said casing through the open side of said casing, a second casing member for completing the casing and holding the above-mentioned parts therewithin, and the joint in the completed casing extending in the same general direction as the plane of movement of said movable switch member.

OLIVER S. JENNINGS. 

